Not exactly the cheapest option but beyond easy to clean and maintain... http://www.walmart.com/ip/Large-Enclosed-Cat-Pan-Colors-May-Vary-Cats/10811473
Wow that seems like a great option!! I'll have to look into those. And do you think bigger birds can use them? Also, it seems like your coop is walk in and you go in to collect the eggs? Wonder if it'd work for outside access nest boxes? Maybe I could take the tops off or use something similar but different?